This invention relates to an epoxy resin composition, and particularly to an epoxy resin composition suitable for forming a solder resist having resistance to electroless plating bath.
Formation of circuit patterns on substrates by electroless copper plating has been conducted, for example, by the following steps (1) to (5):
(1) through-holes are formed in a double-side copper-clad laminate,
(2) PdCl.sub.2 catalyst which is to become a nucleus for plating is coated,
(3) a circuit pattern is formed by etching,
(4) a resist layer is formed on portions other than the through-holes and lands, and
(5) electroless copper plating is conducted on the through-holes and the lands by immersing the laminate in a strongly alkaline electroless copper plating bath heated at 60.degree. to 80.degree. C. with a pH of 12-13.
In such a process, when an epoxy resin composition comprising an epoxide compound, an epoxy-modified guanidine compound obtained by modifying 1-o-tolylbiguamide with an epoxy compound, a filler, a thixotropic agent, an organic solvent, and if necessary an anti-foaming agent is used for forming the resist (U.S. Pat. No. 4,460,718), the usable life (after mixing the major components and a hardener until screen printing of the composition) is as short as about 4 hours and the time of preventing the resist from the corrosion by an electroless copper plating bath is about 20 hours. Therefore, the improvement in both the usable life and the resistance to electroless plating bath has been desired.